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Author Topic: Transfer switches  (Read 4914 times)
white-eagle
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« Reply #15 on: August 03, 2007, 08:59:38 PM »

Tom,a good 50amp transfer switch should cost you between 200 to 300  retail depending where you buy it i am sure you can find cheaper ones.just asking but why are you looking at 100 amp switches

when i looked up auto transfer switches on ebay, iota never came up. 

100 amp is what i was looking for because the generator has 2 50amp breakers and the main bus panel has 100amp.  i realize the shore is 50amp max, but if the generator could put out over that, should'nt i be looking for 100amp???

so i just put in a bid on an iota 50A.  now to replacing
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Tom
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« Reply #16 on: August 04, 2007, 05:40:25 AM »

When we bought our bus the PO had a mechanical transfer switch in the middle bay and it was set up for 30 amp shore power. There was another switch in the coach that transfered power to whichever AC we wanted to use, as we can't run both of them on 30 amp shore power; but, the generator was set up to run both ACs. The PO warned us about connecting shore power while the genny was running. He said it would burn up the genny & that he had done it once already.

Rather than attempting to rewire what was there, I opted to upgrade to 50 amp shore power. I removed all the PO wiring and installed two normally open,100 amp, 3 phase contactors with 120V coils. The outputs from both are tied together and connected to the input of my Square-D 100 amp electrical panel. The input from contactor 1 goes to the output of the generator (2 hots & neutral). The input of contactor 2 goes to shore power. I ran some 14/4 stranded wire to the control panel in the bus to a double pole, double throw switch (ON-OFF-ON). One side of the switch controls the shore contactor & the other side controls the generator contactor, therefore, there is no way to have both on at once. Also, I picked up control voltage for the input side of each contactor so if there is no power present, the contactor cannot be engaged. This system is simple, foolproof, & replacement parts are readily available.

It has worked flawlessly so far.

TOM
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Len Silva
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« Reply #17 on: August 04, 2007, 06:39:24 AM »

Tom,

I think you are on the right track using three pole contactors.  The ones I was refering to are three phase reversing contactors which are mechanically interlocked.  Here's one: http://cgi.ebay.com/ALLEN-BRADLEY-SIZE-TWO-REVERSING-STARTER_W0QQitemZ150146649078QQcmdZViewItem?hash=item150146649078

Len
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Dallas
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« Reply #18 on: August 04, 2007, 06:44:19 AM »

Tom,
I like your idea, and since I plan on adding 50A capability to our old bus, is there a way you can post a wiring diagram of your setup?

I'm not real smart when it comes to electricity.... I still haven't figured out how to get the broken light bulb base out of the lamp without getting zapped! Cheesy
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TomCat
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« Reply #19 on: August 04, 2007, 08:00:33 AM »

I still haven't figured out how to get the broken light bulb base out of the lamp without getting zapped! Cheesy

Dallas,

Stick a raw potato in the socket, and it'll spin the broken base right out!

Jay
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niles500
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« Reply #20 on: August 04, 2007, 08:03:44 AM »

UNPLUG it!
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- Niles
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« Reply #21 on: August 04, 2007, 08:25:33 AM »

Dallas,

I think part of the problem is you do not understand the true nature of "light bulbs".  They don't really emit light, they suck in dark..   This is easily proven.  Shake  new light bulb and you hear nothing, because it has not had a chance to fill with darkness yet.  But if you shake a bulb that no longer works you can usually hear the darkness rattling around inside.

Now if you break the bulb, since the darkness has been pulled inside the bulb it is changed and when it escapes you can't see it.  So, to change the bulb with out getting zapped, turn the reverse polarity switch (which some mistakenly believe is an on/off switch) to the "no longer sucking dark" mode and you should be able to remove the bulb without incident. 

Frank

PS: Remember the ultimate answer is 42
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Dallas
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« Reply #22 on: August 04, 2007, 09:00:23 AM »

Dallas,

I think part of the problem is you do not understand the true nature of "light bulbs".  They don't really emit light, they suck in dark..   This is easily proven.  Shake  new light bulb and you hear nothing, because it has not had a chance to fill with darkness yet.  But if you shake a bulb that no longer works you can usually hear the darkness rattling around inside.

Now if you break the bulb, since the darkness has been pulled inside the bulb it is changed and when it escapes you can't see it.  So, to change the bulb with out getting zapped, turn the reverse polarity switch (which some mistakenly believe is an on/off switch) to the "no longer sucking dark" mode and you should be able to remove the bulb without incident. 

Frank

PS: Remember the ultimate answer is 42

But, Frank...

Doesn't that mean I have to reconfigure the Dilithium Crystals to interface the flux capacitors?

And ...
87 SaftLiner...

When I tried the potato it didn't spin, all I got was a cooked potato!

Niles....

I unplugged the potato, but I still got zapped!
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niles500
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« Reply #23 on: August 04, 2007, 09:06:00 AM »

How many(*) eyes that tater got?  Maybe one of you needs glasses


* Answer: 42
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white-eagle
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« Reply #24 on: August 04, 2007, 10:16:39 AM »

thanks Dallas! 

After some of the comments i made and the questions i've posted about cables, connectors and transfer switches, i was feeling like the most ignorant person on this board.  Grin


after reading your post to dennis about his ground issue on another topic, i'm retracting the above comment.  i am back to being the most ignorant on the board.  Embarrassed  Sad
« Last Edit: August 04, 2007, 10:25:36 AM by manasst » Logged

Tom
1991 Eagle 15 and proud of it.
8V92T, 740, Fulltime working on the road.

Fran was called to a higher duty 12/16/13. I lost my life navigator.
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« Reply #25 on: August 04, 2007, 10:24:16 AM »

You guys are unbelievable!!!!!  Grin Grin Grin Grin Grin Grin

I thought I was confused   Huh Huh BEFORE I joined this board but I was wrong!!

I was just mistaken.... Now I am confused!   Huh Huh Huh

Len, I am not sure but is that type of arrangement used to reverse rotation on 3 phase motors? You could still use it in your application though...... I think!?

Dallas: I can probably post a diagram if you are not in a big hurry. I am looking for a copy of Visio  at a reasonable price unless anyone else has any suggestions for diagramming on a computer.
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Len Silva
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« Reply #26 on: August 04, 2007, 10:50:24 AM »

Len, I am not sure but is that type of arrangement used to reverse rotation on 3 phase motors? You could still use it in your application though...... I think!?

Yes, that's exactly what it is.  Expensive new ($200+) but quite reasonable as used or surplus.

They are basically two - three pole, single throw, normally open contactors with a mechanical interlock.
Len
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Dallas
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« Reply #27 on: August 04, 2007, 11:49:42 AM »

You guys are unbelievable!!!!!  Grin Grin Grin Grin Grin Grin

I thought I was confused   Huh Huh BEFORE I joined this board but I was wrong!!

I was just mistaken.... Now I am confused!   Huh Huh Huh

Len, I am not sure but is that type of arrangement used to reverse rotation on 3 phase motors? You could still use it in your application though...... I think!?

Dallas: I can probably post a diagram if you are not in a big hurry. I am looking for a copy of Visio  at a reasonable price unless anyone else has any suggestions for diagramming on a computer.


Tom,

Check out Google Sketchup and see if that will do what you want. Google gives a light version of it away free, but if you want I have a full version of Sketchup 5 I could make available to anyone who would like it.

http://www.sketchup.com/

Dallas
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DrivingMissLazy
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« Reply #28 on: August 05, 2007, 09:45:07 AM »

Contactors generally have at least one set, and mostly several sets of auxiliary control contacts. I typically use one set of control contacts that are open when the contactor is energized to prevent another contactor or relay or other device from energizing. I really like to use two sets of control contacts. One set normally open and one set normally closed. 100% positive safety control.
Richard
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« Reply #29 on: September 07, 2007, 03:02:55 PM »

Sorry fellas, I'm going to resurrect this thread because Cody started a new one and the answers are here.

Richard and I have spent years working on Automatic Transfer switches and much more complicated equipment...but I believe he'll agree with me...the KISS principle still works all the time.

Contactors, whether manually switched or automatically switched have only one potential for me...when I most need it ...it'll fail and I don't have spare part and/or power!

Take my situation. I have a 50A shore cord (adaptable of course to 30A or 15A depending on what's available) and a 12.5 KW Generator which delivers 50A @ 240VAC. Wow!  A no Brainer!

I have one circuit breaker panel which handles all the 50A 240VAC power I want in the bus.  The main breaker is 50A.  So, why not feed the generator output into a 50A/240VAC receptacle wherein I can simply plug in my shore cord and feed my main panel?

DONE!  FINISHED!  VOILA!

It don't get any easier than that guys!

NCbob
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